Fix partial updates of transparent plugin backgrounds on Mac

chrome/renderer/webplugin_delegate_proxy.cc

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/renderer/webplugin_delegate_proxy.h"
 
 #include <algorithm>
 
 #include "app/gfx/blit.h"
 #include "app/gfx/canvas.h"
@@ skipping 537 matching lines @@
 
   // We're using the native OS APIs from here on out.
 #if WEBKIT_USING_SKIA
   gfx::NativeDrawingContext context = canvas->beginPlatformPaint();
 #elif WEBKIT_USING_CG
   gfx::NativeDrawingContext context = canvas;
 #endif
 
   gfx::Rect offset_rect = rect;
   offset_rect.Offset(-plugin_rect_.x(), -plugin_rect_.y());
+  gfx::Rect canvas_rect = offset_rect;
+#if defined(OS_MACOSX)
+  // The canvases are flipped relative to the context, so flip the rect too.
+  FlipRectVerticallyWithHeight(&canvas_rect, plugin_rect_.height());
+#endif
 
   bool background_changed = false;
   if (background_store_canvas_.get() && BackgroundChanged(context, rect)) {
     background_changed = true;
-    BlitContextToCanvas(background_store_canvas_.get(), offset_rect,
+    gfx::Rect flipped_offset_rect = offset_rect;
+    BlitContextToCanvas(background_store_canvas_.get(), canvas_rect,
                         context, rect.origin());
   }
 
   if (background_changed || !backing_store_painted_.Contains(offset_rect)) {
     Send(new PluginMsg_Paint(instance_id_, offset_rect));
     CopyFromTransportToBacking(offset_rect);
   }
 
-#if defined(OS_MACOSX)
-  FlipRectVerticallyWithHeight(&offset_rect, plugin_rect_.height());
-#endif
   BlitCanvasToContext(context, rect, backing_store_canvas_.get(),
-                      offset_rect.origin());
+                      canvas_rect.origin());
 
   if (invalidate_pending_) {
     // Only send the PaintAck message if this paint is in response to an
     // invalidate from the plugin, since this message acts as an access token
     // to ensure only one process is using the transport dib at a time.
     invalidate_pending_ = false;
     Send(new PluginMsg_DidPaint(instance_id_));
   }
 
 #if WEBKIT_USING_SKIA
@@ skipping 512 matching lines @@
     intptr_t existing_stream, bool notify_needed, intptr_t notify_data) {
   plugin_->InitiateHTTPRangeRequest(url.c_str(), range_info.c_str(),
                                     existing_stream, notify_needed,
                                     notify_data);
 }
 
 void WebPluginDelegateProxy::OnDeferResourceLoading(int resource_id,
                                                     bool defer) {
   plugin_->SetDeferResourceLoading(resource_id, defer);
 }